Method of recovering the meats of bivalves



Feb. 18, 1958 R. D. SEAL, 2,824,004

METHOD OF RECOVERING THE MEATS 0F BIVALVES Filed June 19, 1956 me. a

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In I II ll i l II I] I i ll ll ATTORNEY?" United States Patent METHOD OF RECOVERING THE MEATS OF BIVALVES Roderick D. Seal, Golden Meadow, La., assignor to Blue Channel Corporation, Port Royal, S. C., a corporation of Maryland Application June 19, 1956, Serial No. 592,322

13 Claims. (Cl. 99-111) This invention relates to the treatment of bivalve molluscs typified by oysters, claims, mussels, and scallops and is concerned more particularly with a novel method, by which the meats may be recovered from the shells of such bivalves easily and without damage to the meats. As all the advantages of the method are realized in its use in the treatment of oysters, a form of the method for the recovery of oyster meats will be illustrated and described in detail for purposes of explanation.

In the processing of oysters preparatory to canning, as heretofore practiced, it has been customery to Wash the oysters, when necessary, to remove foreign matter adherent to the shells, after which the oysters are steamed or cooked. For this purpose, the oysters may be loaded into crates, which are then placed in retorts heated by steam, or the oysters may be placed in cars, which are moved into a steam box. The recovery of the oyster meats from the shells requires that the adductor muscles of the oysters be freed from the inner surfaces of the valves and the tenacity with which the muscles adhere to the valves, varies in oysters grown in different localities. Accordingly, the steaming of the oysters as now practiced varies in duration and temperature within a considerable range determined by experience. At the conclusion of the heating operation properly carried on, the shells of the oysters are found to have opened and the adhesionof the muscles to the valves greatly weakened. The meats can then be recovered by manual operations or by the practice of the method described in Harris Patent 2,608,716, issued September 2, 1952.

While the use of the Harris method effects a substantial reduction in cost, it has been found that, in oysters from beds in some localities, such as the Gulf of Mexico, the muscles adhere so tenaciously to the valves, that :the practice of the patented method does not provide as complete a recovery of the meats as is desirable. The present invention is, accordingly, directed to a method of treating oysters and other bivalves, by which a substantially complete recovery of the meats from the shells can be easily obtained at low cost and with little or no damage to the meats, regardless of how tender they may be.

The method of the invention involves heating the ,oysters in two stages, in the first of which the oysters are subjected for a short time to a relatively low temperature well below the boiling point of water. This relatively mild heating causes the shells of the oysters to open slightly and, when this occurs, the second stage ofthe heating is started. In the final heating operation, the oysters are heated to a temperature in excess o'f'212 F. and subjected to that temperaturefor several minutes. At the end of the final stage of the cooking, the meats may be recovered from the shells by agitation as, for example, by tumbling in the apparatus of the Harris Patent 2,6515 88, issued September 22, 1953.

For a better understanding of the invention, reference may be made to the accompanying-drawing, in which Fig. 1 is a view in side elevation of a conventional retort, which may be used in the practice of forms of the methodoftheinvention;

' Fi'gJZ is a sectional view on the line 2--2 of Fig. l; Figs; Fahd 4 areviewsin side elevation and'plan, re-

diameter and the bottom vent and drain 1" to 2",

spectively, of a heating tank, which may be used in the first stage of another form of the method of the invention; and

Fig. 5 is a sectional view on the line 5--5 of Fig. 4.

In the practice of the new method, the shells of the oysters treated should be substantially free of adhering foreign matter and,in some localities, the oysters as landed at the dock require no cleaning, while oysters from other sources should be washed. In most cases, it is desirable to subject the oysters to the shock treatment described in the pending application of Harris identified above and, When the oysters are clean, they may be subjected to shock by dropping them from a substantial height upon a hard surface, while, if the oysters require cleaning, they may be washed and simultaneously subjeoted to shock by being washed in a rotary washer drum of greater than ordinary diameter and provided with bafiles by which the oysters are repeatedly raised and allowed to fall. If the oysters require washing but the shock treatment is not to be used, they may be washed in a conventional rotary washing drum of small diameter, in which they are rolled and tumbled in a mass. 'In both forms of washer, water is sprayed on the oysters by means of spray pipes, as the oysters move through the drum.

The clean oysters, which may or may not have been subjected to shock, are now ready for the first stage of heating of the method of the invention. In carrying out this heating operation, the oysters may conveniently be loaded into the steel crates commonly used in the industry and a number of the crates may then be placed in a standard retort, such as that shown in Figs. 1 and 2. Such a retort includes a steel cylinder 10 and a cover 11 hinged to the cylinder at the upper end th6160f,'S0thalZ the cover can be swung to close or open the top of the cylinder. In closed position, the cover seats upon a gasket 12 and bolts 13 pivoted on the cylinder and receivable between pairs of ears 14 on the cover have-wing nuts 15 engageable with the ears and operable to clamp the cover tight against the gasket. A cross 16 formedof perforated pipes ismounted within the cylinder near the bottom and collars 17 on the pipes and brackets 18 on the inner surface of the cylinder provide supports for the crates. Steam is supplied to the cross through a steam pipe 19 containing a valve 20.

The cylinder is provided near its upper end with a water inlet pipe 21,having a valve .22 and also with an upper steam vent and exhaust pipe 23 with a valve 24;. At its lower end, the cylinder has a lower steam vent and bottom drain pipe v25wit11 a valve 26 and a thermometer 27 and a pressure gauge 28 are mounted on a box 29 open to the interior of the retort and having a small manually-operatedbleeder valve 30. The: cover is provided with a similar bleeder valve 31 and a safety valve 32. The bleeders are of small diameter, such as A", while the top vent and exhaust is usually 1 /2" to 2" in If desired, the retort may be provided with automatic temperature control means.

Inthe use ofthe retort, thecrates of clean oysters are loadedinto the retort and the cover is then swung shut and clamped tight. While the top and bottom vents 23 and 25 are partly open. steamis introduced through the steam supply pipe, so that the interior of the retort is heated to a temperature from F. :to 180 F. fora period of from 1 to 8 minutes. Heating the interior of the retort for about 4 minutes to a temperature about F. is ordinarily satisfactory and, .during thisheating, steam and air escapes through the top vent'and condensate passes away through the bottom vent. After heating as described, the steam supply is increased, so that a pressureof from 1 lb. to 2 lbs. develops :within the re tort within a period of about a minute. At this point,

3 the vents are closed and, with the bleeders 30 and 31 open to permit the escape of occluded air, the steam supply is increased, so that the oysters within the retort are subjected to the final stage of heating.

In the final cooking the oysters are subjected to a temperature ranging from 220 F. to 260 F. at a pressure from 2 /2 lbs. to 20 lbs. for a period of from 4 to 25 minutes. .The duration and temperature of the cooking vary depending upon the characteristics of the oysters, but a final cooking at a temperature of 250 F. at a pressure of 15 lbs. for about 6 to 10 minutes is usually satisfactory. In the cooking operation, the muscles of some of the oysters are freed from the shells and, at the completion of the operation, the top steam vent is opened and the steam supply cut oif. The crates are next removed from the retort and the separation of the meats from the shells is completed by agitation of the meats in the rotary drum disclosed in Harris Patent 2,652,588. In the drum, the oysters are lifted and dropped as the drum rotates and the separated meats escape through openings in the drum wall, while the shells are discharged at the end of the drum.

In another form of the method, the first stage of the heating is effected by means of wet steam. For this purpose, water is introduced into the bottom of a retort,

such as is shown in Fig. 1, to cover the steam distributing pipes 16 to a depth of a few inches and, after the crates of oysters are loaded into the retort, steam is supplied to the pipes 16, while the top vent is open. In 4 or minutes, the water is raised to boiling, whereupon the top vent is closed, the occluded air is permitted to escape through the bleeders, and the first stage of heating is completed. The final cooking is the same as that above described, as, for example, at 250 F. and 15 lbs. pressure for 6 to minutes. At the end of the final stage, the steam is blown off at the top of the retort and the oysters are removed from the retort and subjected to agitation as above described.

In a third form of the method, the oysters in crates are placed in water in a retort or in an open top tank, such as tank 33. This tank contains a pipe coil 34, which is supplied with steam through an inlet pipe 35 with a 36 and has an outlet 37 with a valve 38. The tank has a water inlet pipe 39 with a valve 40 and a drain pipe 41 with a valve 42.

In carrying on the first stage of the heating in the tank 33 or a retort like that shown in Fig. 1, the tank or retort is filled with enough water to cover the oysters, when the filled crates are immersed in the water, and the water is heated to a temperature of 130 F. to 150 F. The crates are then placed in the tank or retort and the oysters left in the hot water for a period of from 3 to 8 minutes. Immersion of the oysters in a bath at 140 F. for a period of about 4 minutes is usually satisfactory. The oysters are then subjected to the final cooking treatment above described and, since the final cooking is at a temperature above 212 F., it cannot be carried out in an open tank but requires the use of a retort or steam box. The recovery of the meats from the oysters is effected by agitation as previously described.

In the different forms of the method, the relatively mild heating in the first stage by dry or wet steam or by hot water appears to have the effect of causing the adductor muscles of the oysters to relax without killing the oysters and the shells open slightly by separation of the valves. Then, when the oysters are subjected to the more severe heating in the second stage, the steam within the heating chamber enters the shells at once and quickly kills the oysters. In the cooking of oysters preliminary to canning, as heretofore practiced, the shells of the oysters are held tightly closed by contraction of the adductor muscles at the start of the heating operation and, even though the oysters may be cooked at a relatively high temperature for a relatively long time, I have found that the separation of the meats from the shells of oysters so cooked cannot always be carried out by agitation of the oysters in bulk in a rotary drum with the desired substantially complete recovery. When the oysters are subjected to the two-stage heating in accordance with the method of the invention, an excellent recovery of the meats can be obtained by agitation and without prolonged tumbling or like treatment, which might result in damage to tender meats.

While I have described the practice of the method with the oysters handled in crates and the heat treatments carried out in a retort or partly in an open top tank and partly in a retort, it is to be understood that other standard equipment may be used. Thus, I may use oyster cars and a steam box, such as are shown in Harris Patent 2,608,716, the box being provided with top and bottom steam vents, a water inlet pipe, and bleeders.

I claim:

1. A method of recovering the meats from bivalves, which comprises subjecting the bivalves to a relatively mild heat treatment, in which the bivalves are maintained at a temperature between about 130 F. and about 180 F. for a period of from 1 to about 8 minutes and until the shells of the bivalves open, then cooking the bivalves by subjecting them to a temperature in the range from about 220 F. to about 260 F. for a period from about 4 to about 25 minutes, subjecting the cooked bivalves in bulk to agitation to separate the meats from the shells, and removing the meats from contact with the shells.

2. The method of claim 1, in which the bivalves are oysters.

3. The method of claim 2, in which the mild heat treatment is carried on by the use of live steam and, during such treatment, the oysters are maintained at a temperature in the range from about 1.35 F. to about 180 F. for a period of about 1 to about 8 minutes.

4. The method of claim 3, in which, in the mild heat treatment, the oysters are maintained at about 160 F. for about 4 minutes.

5. The method of claim 1, in which, during the mild heat treatment, the bivalves are confined within an enclosed space, the enclosed space is initially vented to the atmosphere at top and bottom, steam is introduced into the enclosed space to expose the bivalves to a tempera--' ture in the range from about 135 F. to about 180 F. for a period of about 1 to about 8 minutes, the vents are then closed, and steam is introduced into the enclosed space at an increased rate to cook the bivalves.

6. The method of claim 1, in which the mild heat treatment is carried on by confining the bivalves in an enclosed space with a quantity of water and discharging steam into the water to raise it to boiling temperature.

7. The method of claim 6, in which the bivalves are oysters.

8. The method of claim 7, in which water is raised to the boiling temperature in about 4 to 5 minutes.

9. The method of claim 1, in which the mild heat treatment is carried on by immersing the bivalves for a period of from about 3 to 8 minutes in a hot liquid at a temperature within the range from about F. to about 150 F.

10. The method of claim 9, in which the bivalves are oysters.

11. The method of claim 10, in which the hot liquid is at a temperature of about F. and the immersion time is about 4 minutes.

12. The method of claim 1, in which the bivalves are cooked at a temperature of about 250 F. for about 6 to 10 minutes.

13. The method of claim 12, in which the bivalves are oysters.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF RECOVERING THE MEATS FROM BIVALVES, WHICH COMPRISES SUBJECTING THE BIVALVES TO A RELATIVELY MILD HEAT TREATMENT, IN WHICH THE BIVALVES ARE MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 130*F. AND ABOUT 180* F. FOR A PERIOD OF FROM 1 TO ABOUT 8 MINUTES AND UNTIL THE SHELLS OF THE BIVALVES OPEN, THEN COOKING THE BIVALVES BY SUBJECTING THEM TO A TEMPERATURE IN THE RANGE FROM ABOUT 220*F. TO ABOUT 260*F. FOR A PERIOD FROM ABOUT 4 TO ABOUT 25 MINUTES, SUBJECTING THE COOKED BIVALVES IN BULK TO AGITATION TO SEPARATE THE MEATS FROM THE SHELLS, AND REMOVING THE MEATS FROM CONTACT WITH THE SHELLS. 